Growth of crustose lichens : a review

Crustose species are the slowest growing of all lichens. Their slow growth and longevity, especially of the yellow-green Rhizocarpon group, has made them important for surface-exposure dating (lichenometry). This review considers various aspects of the growth of crustose lichens revealed by direct measurement including: 1) early growth and development; 2) radial growth rates (RGR, mm yr−1); 3) the growth rate–size curve; and 4) the influence of environmental factors. Many crustose species comprise discrete areolae that contain the algal partner growing on the surface of a non-lichenized fungal hypothallus. Recent data suggest that 'primary' areolae may develop from free-living algal cells on the substratum while 'secondary' areolae develop from zoospores produced within the thallus. In more extreme environments, the RGR of crustose species may be exceptionally slow but considerably faster rates of growth have been recorded under more favourable conditions. The growth curves of crustose lichens with a marginal hypothallus may differ from the 'asymptotic' type of curve recorded in foliose and placodioid species; the latter are characterized by a phase of increasing RGR to a maximum and may be followed by a phase of decreasing growth. The decline in RGR in larger thalli may be attributable to a reduction in the efficiency of translocation of carbohydrate to the thallus margin or to an increased allocation of carbon to support mature 'reproductive' areolae. Crustose species have a low RGR accompanied by a low demand for nutrients and an increased allocation of carbon for stress resistance; therefore enabling colonization of more extreme environments

The development of an Afrikaans test for sentence recognition thresholds in noise

OBJECTIVE: The development of a valid and reliable Afrikaans test of sentence recognition thresholds in noise. DESIGN: A collection of sentences was developed, rated for naturalness and grammatical complexity, and digitally recorded using a female speaker. Sentences found to have similar psychometric curve slopes, with equivalent intelligibility at three different noise levels, were arranged into 22 phonemically matched lists of ten sentences each. List equivalence was evaluated in normal-hearing listeners in full and reduced bandwidth conditions. Test-retest reliability of the remaining lists was evaluated in a second group of listeners. STUDY SAMPLE: All listeners were native speakers of Afrikaans with normal hearing. For evaluation of list equivalence, ten listeners were used. Twenty other listeners were used to evaluate test-retest reliability. RESULTS: A collection of eighteen phonemically matched lists was produced. Lists were found to be of equivalent difficulty in full and reduced bandwidth conditions, and to have good test-retest reliability in normal-hearing listeners. The average recognition threshold of these lists was -2.73 dB signal-to-noise ratio (standard deviation = 0.64 dB), and within-subject variability was 1.22 dB. CONCLUSIONS: The developed test provides a valid and reliable means of measuring sentence recognition thresholds in noise in Afrikaans.This project was financially supported by the National Research Foundation of South Africa

First T2K measurement of transverse kinematic imbalance in the muon-neutrino charged-current single-π⁺ production channel containing at least one proton

This paper reports the first T2K measurement of the transverse kinematic imbalance in the single-π+ production channel of neutrino interactions. We measure the differential cross sections in the muon-neutrino charged-current interaction on hydrocarbon with a single π+ and at least one proton in the final state, at the ND280 off axis near detector of the T2K experiment. The extracted cross sections are compared to the predictions from different neutrino-nucleus interaction event generators. Overall, the results show a preference for models that have a more realistic treatment of nuclear medium effects including the initial nuclear state and final-state interactions

Measurements of <i>ν̅</i>_{<i>μ </i>}and<i>ν̅</i>_<i>μ</i> + ν_μ charged-current cross-sections without detected pions or protons on water and hydrocarbon at a mean anti-neutrino energy of 0.86 GeV

We report measurements of the flux-integrated |$\overline{\nu}_\mu$| and |$\overline{\nu}_\mu+\nu_\mu$| charged-current cross-sections on water and hydrocarbon targets using the T2K anti-neutrino beam with a mean beam energy of 0.86 GeV. The signal is defined as the (anti-)neutrino charged-current interaction with one induced |$\mu^\pm$| and no detected charged pion or proton. These measurements are performed using a new WAGASCI module recently added to the T2K setup in combination with the INGRID Proton Module. The phase space of muons is restricted to the high-detection efficiency region, |p_{\mu}>400~{\rm MeV}/c| and |\theta_{\mu}<30^{\circ}|⁠, in the laboratory frame. An absence of pions and protons in the detectable phase spaces of |p_{\pi}>200~{\rm MeV}/c|⁠, |\theta_{\pi}<70^{\circ}| and |p_{\rm p}>600~{\rm MeV}/c|⁠, |\theta_{\rm p}<70^{\circ}| is required. In this paper, both the |$\overline{\nu}_\mu$| cross-sections and |$\overline{\nu}_\mu+\nu_\mu$| cross-sections on water and hydrocarbon targets and their ratios are provided by using the D’Agostini unfolding method. The results of the integrated |$\overline{\nu}_\mu$| cross-section measurements over this phase space are |$\sigma_{\rm H_{2}O}=(1.082\pm0.068(\rm stat.)^{+0.145}_{-0.128}(\rm syst.)) \times 10^{-39}\,{\rm cm^{2} / nucleon}$|⁠, |$\sigma_{\rm CH}=(1.096\pm0.054(\rm stat.)^{+0.132}_{-0.117}(\rm syst.)) \times 10^{-39}\,{\rm cm^{2} / nucleon}$|⁠, and |$\sigma_{\rm H_{2}O}/\sigma_{\rm CH} = 0.987\pm0.078(\rm stat.)^{+0.093}_{-0.090}(\rm syst.)$|⁠. The |$\overline{\nu}_\mu+\nu_\mu$| cross-section is |$\sigma_{\rm H_{2}O} = (1.155\pm0.064(\rm stat.)^{+0.148}_{-0.129}(\rm syst.)) \times 10^{-39}\,{\rm cm^{2} / nucleon}$|⁠, |$\sigma_{\rm CH}=(1.159\pm0.049(\rm stat.)^{+0.129}_{-0.115}(\rm syst.)) \times 10^{-39}\,{\rm cm^{2} / nucleon}$|⁠, and |$\sigma_{\rm H_{2}O}/\sigma_{\rm CH}=0.996\pm0.069(\rm stat.)^{+0.083}_{-0.078}(\rm syst.)$|⁠

Improved constraints on neutrino mixing from the T2K experiment with 3.13 x 10²¹ protons on target

The T2K experiment reports updated measurements of neutrino and antineutrino oscillations using both appearance and disappearance channels. This result comes from an exposure of 14.9(16.4)×1020 protons on target in neutrino (antineutrino) mode. Significant improvements have been made to the neutrino interaction model and far detector reconstruction. An extensive set of simulated data studies have also been performed to quantify the effect interaction model uncertainties have on the T2K oscillation parameter sensitivity. T2K performs multiple oscillation analyses that present both frequentist and Bayesian intervals for the Pontecorvo-Maki-Nakagawa-Sakata parameters. For fits including a constraint on sin2θ13 from reactor data and assuming normal mass ordering T2K measures sin2θ23=0.53-0.04+0.03 and Δm322=(2.45±0.07)×10-3  eV2 c-4. The Bayesian analyses show a weak preference for normal mass ordering (89% posterior probability) and the upper sin2θ23 octant (80% posterior probability), with a uniform prior probability assumed in both cases. The T2K data exclude CP conservation in neutrino oscillations at the 2σ level

Measurement of the νμ\nu_{\mu} charged-current cross sections on water, hydrocarbon, iron, and their ratios with the T2K on-axis detectors

We report a measurement of the flux-integrated $\nu_{\mu}$ charged-current cross sections on water, hydrocarbon, and iron in the T2K on-axis neutrino beam with a mean neutrino energy of 1.5 GeV. The measured cross sections on water, hydrocarbon, and iron are $\sigma^{\rm{H_{2}O}}_{\rm{CC}}$ = (0.840$\pm 0.010$(stat.)$^{+0.10}_{-0.08}$(syst.))$\times$10$^{-38}$cm$^2$/nucleon, $\sigma^{\rm{CH}}_{\rm{CC}}$ = (0.817$\pm 0.007$(stat.)$^{+0.11}_{-0.08}$(syst.))$\times$10$^{-38}$cm$^2$/nucleon, and $\sigma^{\rm{Fe}}_{\rm{CC}}$ = (0.859$\pm 0.003$(stat.) $^{+0.12}_{-0.10}$(syst.))$\times$10$^{-38}$cm$^2$/nucleon respectively, for a restricted phase space of induced muons: $\theta_{\mu}<45^{\circ}$ and $p_{\mu}>$0.4 GeV/$c$ in the laboratory frame. The measured cross section ratios are ${\sigma^{\rm{H_{2}O}}_{\rm{CC}}}/{\sigma^{\rm{CH}}_{\rm{CC}}}$ = 1.028$\pm 0.016$(stat.)$\pm 0.053$(syst.), ${\sigma^{\rm{Fe}}_{\rm{CC}}}/{\sigma^{\rm{H_{2}O}}_{\rm{CC}}}$ = 1.023$\pm 0.012$(stat.)$\pm 0.058$(syst.), and ${\sigma^{\rm{Fe}}_{\rm{CC}}}/{\sigma^{\rm{CH}}_{\rm{CC}}}$ = 1.049$\pm 0.010$(stat.)$\pm 0.043$(syst.). These results, with an unprecedented precision for the measurements of neutrino cross sections on water in the studied energy region, show good agreement with the current neutrino interaction models used in the T2K oscillation analyses